Start to add annotations to the cpu_info members, doing I/a/o for

Start to add annotations to the cpu_info members, doing I/a/o for
immutable/atomic/owned ala <sys/proc.h>.  Move CPUF_USERSEGS and
CPUF_USERXSTATE, which really are private to the CPU, into a new
ci_pflags and rename s/CPUF_/CPUPF_/.  Make all (remaining) ci_flags
alterations via atomic_{set,clear}bits_int(), so its annotation
isn't a lie.  Delete ci_info member as unused all the way from
rev 1.1

ok jsg@ mlarkin@